Switch for electric knife with wiping action contact shorting bar

ABSTRACT

The invention is directed to an electric slicing knife with improved switch structure wherein no movable leads are employed in opening and closing the switch and the parts of the switch are constructed and arranged to avoid the need for precise alignment and permitting automatic assembly. A pivotal switch actuator supports an L-shaped shorting contact with slots struck in it and directed toward the pivot. Thereby the closing distance between the shorting bar and stationary contacts is minimized while the moment arm required to close the actuator is maximized. This gives maximum contact scrubbing action with minimum force.

United States Patent Freeman et a1.

[ SWITCH FOR ELECTRIC KNIFE WITH [15] 3,694,604 1451 Sept. 26, 1972 3,392,250 7/l968 Ziegler et al. ..200/164 R X WIPING ACTION CONTACT SHORTING BAR Primary Examiner-Robert K. Schaefer [72] Inventors: Arthur ll. Freeman; Giacinto Valjffgfgffiz'xizggz g izigxz azf J Plan lone, both of Brockport, NY. and John F. Cullen [73] Assignee: General Electric Company 22 Filed: April 9, 1971 [57] ABSTRACT The invention is directed to an electric slicing knife [211 App! 132702 with improved switch structure wherein no movable leads are employed in opening and closing the switch [52] US. Cl "200/157, 200/164 R, 200/166 BH and the parts of the switch are constructed and ar [51] Int. Cl ..Hlh 23/12, l-lOlh 9/06, l-lOlh 1/ l8 ranged to avoid the need for precise alignment and [58] Field of Search...200/157, 164, 159 R, 6 R, 6 C, permitting automatic assembly.

ZOO/166 166 D A pivotal switch actuator supports an L-shaped short- [56] Ref ren es Cit d ing contact with slots struck in it and directed toward e c e the pivot. Thereby the closing distance between the UNITED STATES PATENTS shorting bar and stationary contacts is minimized while the moment arm required to close the actuator 3,308,535 3/l967 Freeman et a1 "ZOO/157 X is maximized. This gives maximum contact scrubbing 3,529,109 9/1970 Cross ..200/6 R X action with minimum force 3,358,108 12/1967 Hansen ..200/157 3,474,204 1969 Cork ....200/ 164 R 3 Claims, 3 Drawing Figures l l 44 l I r 1| I 1 i I .74 30 32 Z 54 Ill/1 X 2A SWITCH FOR ELECTRIC KNIFE WITH WIPING ACTION CONTACT SHORTING BAR BACKGROUND OF THE INVENTION 1. Field of the Invention The invention is directed to an electric slicing knife having improved switch structure which avoids any movable leads during switch operation and uses parts that do. not require precise alignment thus reducing the cost and permitting automatic assembly.

2. Description of the Prior Art 7 In the present manufacture of household appliances, there is a never-ending search to reduce costs, simplify the parts, make the appliance more reliable for long life, and design it for automation as much as possible in order to further reduce costs. The electric slicing knife is now a well-known appliance that has achieved wide usage. It is generally controlled by a finger-operated switch that has means to ensure against inadvertent actuation by providing a safety lock. A typical knife is shown in US. Pat. No. 3,308,535 of common assignment. One of the difficulties in such knives has been the constant flexing of the lead from the motor to the switch by virtue of the construction generally used. While not frequent, the constant flexing tends to weaken and break the lead after long usage. Additionally, in any two electrical contacts that make-andbreak repeatedly there is a tendency for the surfaces to become oxidized after long use thus hindering the switching action. It is known to use nonmovable or fixed contacts to avoid flexing leads and it is generally common to use a wiping action in electrical contacts so that a sliding motion scrubs or cleans the surfaces as the contacts come together. Such cleaning is shown in Patent No. 3,348,116 of common assignment. As the knife has been improved, it has been found desirable to redesign the switch structure to simplify it, reduce the cost, improve the operation, and avoid the need for precise assembly so that the part may be machine-assembled or the manufacture may be automated.

SUMMARY OF THE INVENTION Briefly described, the invention is directed to an electric slicing knife with a hollow handle and a motor therein having forwardly extending cutting means in the form of blades driven by the motor. An improved switch means is provided that utilizes an elongated movable switch actuator that is disposed longitudinally in the handle and is spring-pivoted at one end in the handle and normally biased opened. A pair of spaced contacts is fixedly secured in the handle and the motor is lead-connected to each of the fixed contacts so that no lead wires are flexed. A resilient generally L-shaped shorting bar is held by one leg in the actuator at the end opposite the pivot and the other leg of the shorting bar has longitudinal slots struck in the bar and extending toward the pivot whereby the shorting bar bridges the contacts on switch closing. The slots define independent spaced spring portions for each contact and are aligned to wipe the contact on engagement whereby the leads are unflexed and the switch operates to independently clean and seat on the contacts on each actuation without any precise alignment between the contacts and shorting bar. A transversely biased and movable safety button is disposed in a hollow portion of the actuator to block and unblock pivotal rotation of the actuator. Various of the parts are non-removably mounted by barbed locking means for easier automation. Thus, the main object of the invention is to provide an improved switching structure in an electric slicing knife.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENT While the improved switch structure could generally be used in many applications, the particular embodiment lends itself well to the electric slicing knife and it will be described in connection therewith.

Referring to FIG. 1, there is shown an electric slicing knife that includes a hollow, elongated housing or handle 10 generally made in the form of an upper and lower casing shaped to provide a hand grip for the user. A pair of forwardly extending cutting blades 12 extends from the forward end of the handle and is releasably connected thereto. A motor and drive unit (not shown) are enclosed within the handle 10 and blades 12 are releasably connected to the drive unit in a well-known manner. The knife is controlled by a trigger-like switch means 14 that is normally biased open and actuated by the finger of the user as he grips the handle 10.

Referring next to FIGS. 2 and 3, the details of the switch mechanism 14 are shown. They include an actuator 16 that is substantially hollow and preferably of molded plastic. For trigger action, the actuator is longitudinally disposed in opening 18 in the lower portion of handle 10 and is held therein by spring 20 that acts as a pivot by being barb-connected in slot 22 in the actuator at one end. The spring is fastened to the handle by a suitable snap or slide connection with projection 24 on retainer guide 26 through which the driving mechanism for the knife blades reciprocates in a wellknown manner. As seen in FIG. 2, in order to hold the parts together, projection 24 extends through a recess 28 in the molded lower portion of handle 10 and the forward portion of spring 20 slides through the projection 24 whereupon an opening 30 in the spring snaps over post 32 to lock the spring in position. The rear portion of actuator 16 is held in the opening 18 by flange 34 locking over the rear portion of the opening. Consequently, the actuator is spring-pivoted and normally biased open with the closing force applied by the forefinger of the user in the direction of the arrow as shown.

In order to complete the circuit and actuate the motor and thus the cutting blades, a pair of spaced contacts 36 is provided and these are fixedly secured in molded slots 38 in handle 10. The fixed contacts 36 are L-shaped as shown and barbed to slide in slots 38 and lock therein with projecting ends 40 extending down into opening 42 below the molded portion in the bandle. Suitable leads 44 from the motor are connected to the fixed contacts and do not move or flex.

In order to complete the circuit and bridge the projecting ends 40 of contacts 36, a generally L-shape resilient shorting bar 46 is provided and carried by actuator 16 by having one barbed leg 48 extend and lock in slot 50 at the opposite end from pivot in actuator 16. It should. be apparent that the barbed locking means for the contacts, the shorting bar, and the spring pivot render them nonremovable and adaptable to machine assembly since the parts are merely pressed together.

Because of the desire to automate, it is preferred that precise alignments be avoided and to this end, shorting bar 46 has a pair of longitudinal slots 52 struck in the shorting bar and directed toward spring pivot 20. The resiliency of the shorting bar in combination with the slots defines independent spaced spring portions 54 that abut projection 40 of each contact thus making them independently adjustable when the actuator is closed and contacts 36 are bridged. Thus, flexibility is permitted without precise alignment between the shorting bar and the contacts.

In order to avoid oxidation and poor contacts, the spring portion 54 may be slightly bent or aligned so that there is a wiping or scrubbing action as the portions 54 and projections 40 abut thus ensuring a clean and posi tive electrical contact at all times. The cleaning action is enhanced by causing the wiping to occur over a longer distance as actuator 16 is pivoted about 20. At the same time, a minimum switching force is ensured by lengthening the moment arm between the users finger and pivot 20. Both of these actions are obtained by striking the slots in shorting bar 54 so that the bar is directed toward the pivot whereby the closing distance between portions 54 and projections 40 is minimized while the moment arm required to close the actuator is maximized as will be apparent from FIG. 2. This gives the maximum scrubbing action with the minimum amount of actuator force in the direction of the arrow of FIG. 2.

A safety means is provided to prevent closing of the contacts and inadvertent knife operation and this is shown and described in the referenced US, Pat. No. 3,308,535 and comprises essentially a plastic leaf spring 56 disposed in the hollow portion of the actuator and carrying a button 58 whereby the button is transversely movable and is biased by spring 56 to snap from one side of the actuator to the other and block and unblock pivotal rotation of the actuator as described in said US. Pat. No. 3,308,5 35. While the resiliency of plastic leaf spring 56 is generally sufficient to maintain it within its cavity, the provision of shorting bar 46 extending toward pivot'20 extends over the end of spring 56 as shown in FIG. 2 and is a back-up means to retain the spring therein.

The switch structure described avoids any flexing of electrical leads by connecting those leads to fixed contacts and completion of the circuit is by the unique shorting bar arrangement which is independently adjustable for each contact by its slotted construction. Its orientation in the actuator provides for a minimum actuating force with maximum cleaning action between the fixed contacts and the shorting bar. The bar also acts as a retainer for the spring on the safety means. Each of the parts permits of machine assembly by using no fastene d avoidi e r cise ali nm t normally requii e whereby t e arlih and pr sse -in construction lends itself to automation.

While there has been shown a preferred form of the invention, obvious equivalent variations are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practised, otherwise then as specifically described, and the claims are intended to cover such equivalent variations.

We claim:

1. In an electric slicing knife having a hollow handle with a motor therein and forwardly extending cutting means driven thereby, improved switch means comprising,

an elongated longitudinally disposed movable switch actuator spring-pivoted at one end in said handle for finger actuation and normally biased open,

a pair of spaced contacts fixedly secured in said handle,

said motor being lead-connected to each of said fixed contacts,

a resilient L-shaped shorting bar to bridge said contacts on switch closing and having one leg held in said actuator at the end opposite said pivot and the other leg extending longitudinally along said actuator toward said pivot, said bar having slots therein to define an independent spaced spring portion for each contact,

said slots being longitudinally struck in said bar toward said pivot to minimize the switch closing distance while maximizing the closing moment on said actuator,

whereupon said leads are unflexed and said switch operates to independently clean and seat on said contacts on each actuation without precise alignment therebetween, and

operable safety means to prevent closing of said contacts.

2. Apparatus as described in claim 1 wherein said actuator is substantially hollow and said safety means includes a transversely movable biased button generally disposed in said hollow and movable to block and unblock pivotal rotation of said actuator.

3. Apparatus as described in claim 2 wherein each of said contacts, shorting bar, and spring pivot are nonremovably mounted by a pressed-in barbed locking means. 

1. In an electric slicing knife having a hollow handle with a motor therein and forwardly extending cutting means driven thereby, improved switch means comprising, an elongated longitudinally disposed movable switch actuator spring-pivoted at one end in said handle for finger actuation and normally biased open, a pair of spaced contacts fixedly secured in said handle, said motor being lead-connected to each of sAid fixed contacts, a resilient L-shaped shorting bar to bridge said contacts on switch closing and having one leg held in said actuator at the end opposite said pivot and the other leg extending longitudinally along said actuator toward said pivot, said bar having slots therein to define an independent spaced spring portion for each contact, said slots being longitudinally struck in said bar toward said pivot to minimize the switch closing distance while maximizing the closing moment on said actuator, whereupon said leads are unflexed and said switch operates to independently clean and seat on said contacts on each actuation without precise alignment therebetween, and operable safety means to prevent closing of said contacts.
 2. Apparatus as described in claim 1 wherein said actuator is substantially hollow and said safety means includes a transversely movable biased button generally disposed in said hollow and movable to block and unblock pivotal rotation of said actuator.
 3. Apparatus as described in claim 2 wherein each of said contacts, shorting bar, and spring pivot are non-removably mounted by a pressed-in barbed locking means. 